This thesis is comprised of three chapters. In the first two I analyze how fertility decisions and the presence of young children in the household affect the labor supply of women on the intensive margin and their labor market allocation across different types of work such as formal, informal and self-employment. To do so, I use Brazilian data, motivated by the relative rigidity of the labor legislation in Brazil, the high prevalence of informal work and the scarcity of part-time jobs in the formal sector. In the first chapter I specify a reduced-form, dynamic discrete choice model of sequential labor supply decisions in two margins, labor force participation and work in the formal sector. I use longitudinal household survey data representative of the Brazilian population for the years 2012-2017 to estimate the model. The results show that, among low-education women, observed fertility is endogenous with respect to the decision to work in the formal sector, and that the presence of children in the household has a significant negative effect on the probability of having a formal job conditional on labor force participation. No such evidence is found for college-educated women. In light of these results, in the following chapter I develop an estimable structural model of life-cycle labor supply and fertility decisions and estimate it using data for the years 2002-2015. I then perform counterfactuals on the estimated model in order to isolate the effect of fertility on female labor market informality and to show the partial equilibrium effects of increasing the availability of part-time work in the formal sector and of increasing the duration of maternity leave. In the third chapter, I present a new approach to handle the initial conditions problem in dynamic binary choice models with individual unobserved heterogeneity. I assess the performance of my method relative to existing approaches using a set of simulation experiments and show that it displays relatively better precision and only slightly worse accuracy.